1. Filed of the Invention
The present invention relates to a method for promoting adhesion of ultra high modulus a composite consisting of polyethylene (UHMPE) fibers and vinyl ester resins. More particularly, the present invention relates to a process for promoting adhesion of a UHMPE fiber/vinyl ester resin composite.
2. Description of the Prior Art
Ultra high modulus polyethylene fibers having a density of 2/3 of Kevlar fiber and 1/2 of carbon fiber represent a high specific strength [see, 30th National SAMPE Symposium, p. 280, 1985]. Due to this property, ultra high modulus polyethylene fibers have been used in helicopter pannel, airplain interior material, tennis racket, ski, golf club and other various structural material [see, 32nd International SAMPE Symposium, p. 230, 1987].
However, it has been reported that in the case of using the ultra high modulus polyethylene fibers in composites, delamination at the interface between the fibers and the matrix resins happens due to poor reactivity between the fibers and the matrix resins; thereby the physical properties of composites become lowered [see, 33rd International SAMPE Symposium, p. 721, 1988].
As an approach to overcome the above disadvantages, several methods have been proposed. In accordance with one of these methods, the reactivity of the fibers with the matrix resins is enhanced by subjecting the surface of the fibers to a cold plasma etching treatment [see, 33rd International SAMPE Symposium, p 551, 1988]. However, these methods suffer from the disadvantages that the functional groups on the modified surface of the fibers are deteriorated rapidly with the lapse of time and their reactivity with the matrix resins become lowered accordingly.
Another approach was the chemical treatment where the surface of ultra high modulus polyethylene fibers is modified by a chromic acid solution of strong oxidizer [see, Composite Interfaces, p. 37, 1986]. However, this method may render the strength of the fiber degraded by chromic acid used, and the waste liquids from this method may result in the pollution of environment.